During construction or repair of electrical systems, it may be necessary to join two cables together. Heat shrink kits that utilize heat shrink tubing can be used to join the two cables together. Heat shrink kits can be splice kits or cold-lead kits. Splice kits can utilize soldering to connect two identical cables. Cold-lead kits utilize mechanical connectors which may have crimp connections. Once the cables are joined together, there may be exposed wires or mechanical connectors in between insulated sections of the two cables. The exposed section can be covered with heat shrink tubing, which can provide a barrier against moisture as well as electrical insulation.
Heat shrink tubing can include an adhesive lining. Adhesive lined heat shrink tubing is ubiquitous, and is an effective moisture sealer and electrical insulator. Its moisture sealing properties can be improved with the addition of mastic tape when the tape is wrapped around wires and connectors prior to shrinking the tubes. However, being polymeric in construction, the heat shrink tubing's resistance to impact such as cold impact (typically −20° C.) and flammability is limited, even when the tubing contains flame retardants. In many applications, resistance to impact and/or flammability is of great concern. For example, following changes to IEC standard 62395-2-1 to Edition 2, flammability and impact resistance are now required for heat shrink kits for electrical resistance trace heating systems. However, end users may desire a heat shrink kit with resistance to impact and/or flammability for use with any type of cable.
Past heat shrink kits have failed to provide impact resistance and/or flammability resistance. It has been empirically observed in impact testing of splice kits versus cold lead type kits that cold-lead kits are more prone to impact damage. It is believed this is because cold lead kits have air gaps (voids) beneath the heat shrink tubing due to the size and shape differences of the cold lead compared to the heating cable. In contrast, splice kits, where two identical pieces of heating cable are joined, have little or no air gap, and are almost a solid mass. The solid construction may reduce damage due to impact by providing better support and lower impact pressure compared to the cold lead kit. However, both splice kits and cold lead kits can fail to provide flammability resistance due to the polymeric nature of heat shrink tubing.
Methods other than heat shrink kits can provide impact resistance and/or flammability resistance, all with drawbacks. For example, one current solution is a splice kit including a metal shell sealed with Room-Temperature-Vulcanizing (RTV) silicone sealant and mechanical connectors. This method can provide impact and flammability resistance, but can be messier and more difficult to use than heat shrink kits. Other approaches involve non-heat shrink mechanical kits that are much more costly than heat shrink kits.